1. Field of the Invention
The present invention relates to a process for preparing nanoporous VSB-5 molecular sieves, and more particularly, to a process for preparing nanoporous VSB-5 molecular sieves useful as a hydrogen storage material, a catalyst, a catalyst supporter and an adsorbent, performed in such a manner that low-cost inorganic base or monoamine instead of a template essential in the conventional process is, as a pH modifier, incorporated into raw materials comprised of nickel and phosphorous compounds and crystallized to give VSB-5 molecular sieves in an economical and efficient manner.
2. Description of the Related Art
A nanoporous material of nickel and phosphorous, the so-called VSB-5 molecular sieve with pore openings composed of 24-membered ring of oxygen atoms has pores of about 6.4 Å, exhibits a catalytic activity for selective hydrogenation and dehydrogenation, and shows relatively higher thermal stability. Therefore, the VSB-5 molecular sieve has been highlighted as a porous solid inorganic material standing comparison with conventional zeolitic molecular sieves.
However, the synthesis procedures for VSB-5 molecular sieve have not been suggested yet in diverse manners. The representing process comprises the addition of the diamine bases from 1,2-ethylene diamine to 1,8-octane diamine to nickel and phosphorous compounds (J. Am. Chem. Soc., 125:1309-1312(2003); and Angew. Chem. Int. Ed., 40:2831-2834(2001)). As the diamine base, 1,3-diaminopropane (DAP) is mainly employed. The composition of VSB-5 molecular sieve includes as mole ratio of about 1.0 Ni: 2.1 P: 5.0 DAP: 140 H2O, which undergoes a hydrothermal reaction for 5-6 days at 180° C. to yield VSB-5 molecular sieve. However, the diamines used a base are generally expensive and requires heat treatment for the removal of amines after the synthesis of VSB-5 molecular sieve. Furthermore, the heat treatment results in the disruption or occlusion of pore structures of VSB-5 molecular sieve, which highly decreases the surface area of VSB-5 molecular sieve to exhibit the reduced efficiency on its application.
Therefore, there remains a need in the art for the development of a novel process for preparing VSB-5 molecular sieve by use of low-cost amines, not requiring the heat treatment.